The project outlined in this proposal will allow Dr. David Stachura, a 4th year postdoctoral fellow in Dr. David Traver's lab at the University of California San Diego to develop and refine novel methods to study hematopoietic stem and progenitor cell development and their subsequent dysregulation during hematopoietic disease. Furthermore, the career development outlined in this proposal will allow Dr. Stachura to transition from a mentored scientific position to an independent research career at a major research institution. Dr. David Stachura performed his thesis work in the laboratory of Mitchell Weiss at the University of Pennsylvania studying transcriptional regulation of hematopoiesis and it's dysregulation in acute megakaryoblastic leukemia. Dr. Stachura has taken the expertise developed as a graduate student to his postdoctoral laboratory, where he has been investigating hematopoietic development in the zebrafish model system in the lab of Dr. David Traver, an innovator in the field of zebrafish hematopoiesis and immunology. The zebrafish is an excellent vertebrate system to study blood development;they are optically transparent, fecund, and genetically amenable, explaining their utility in studying blood development and disorders. Importantly, zebrafish have served as a model organism to study human disease, as their blood system is nearly identical to mouse and human. However, the zebrafish as a model system has a major weakness;a paucity of in vitro short term assays to identify and further study hematopoietic stem and progenitor cell differentiation potential and dysregulation. In a relatively short time, Dr. Stachura developed methods to study zebrafish hematopoietic development in vitro, and seeks to further refine these studies while mentored in the Traver laboratory. His short-term research goals are to further develop these novel in vitro assays, which will lead to a greater understanding of the molecular processes controlling normal hematopoietic development. The long-term goal of this application is to identify and characterize hematopoietic stem and progenitor cells in the embryo and adult zebrafish with these novel assays in the hope of understanding the normal differentiation processes that are co-opted during hematolymphoid disease development. The end goal is to foster Dr. Stachura's development into a successful independent researcher focused on understanding the molecular basis of vertebrate hematopoietic lineage restriction and development. First, Dr. Stachura will refine and optimize in vitro assays for zebrafish hematopoietic cells. Interrogating the hematopoietic niche will be performed to discover new cytokines and signaling molecules important in the production, maintenance, and differentiation of mature erythroid, myeloid, and lymphoid cells. After identifying and producing critical factors responsible for the regulation of hematopoiesis, clonal assays to examine individual progenitor cells will be developed and refined. This refinement of clonal assays will be utilized to identify, examine, and characterize embryonic and adult lineage restricted progenitors in the zebrafish for the first time. The experiments proposed in this application will allow the further study of normal and dysregulated progenitor cells, offering unparalleled precision in analyzing the etiology of hematopoietic disease in a model organism that is similar to mammals, but far more genetically amenable. Dr. Traver's laboratory at UCSD is an excellent training environment to perform these studies, as he is a young, innovative leader in the field of murine and zebrafish immunology and hematopoiesis instrumental in generating the first zebrafish model of leukemia. Dr. Traver's professional awards are numerous, he has just been awarded tenure, and the laboratory is well funded, containing all necessary supplies and equipment for successful completion of this project. As a former recipient of a K01 career development award, Dr. Traver has the necessary knowledge to see Dr. Stachura's career development to fruition. Dr. Stachura will meet and present work regularly to experts in the fields of development, immunology, hematology, and leukemia, aiding in the development of his project development and speaking skills. Dr. Stachura will also present his data to a formal mentorship committee comprised of senior experts in his field of study that will aid his development into an independent researcher. UCSD offers numerous pedagogical courses that Dr. Stachura will attend, as well as seminars on career development and a managerial lab symposium administered by the Office of Postdoctoral Affairs. Working closely with experts in the field of hematology will allow Dr. Stachura to develop this project to a level where he will be able to succeed as an independent researcher. The vibrant, collaborative scientific atmosphere of talented experts in the field of hematopoiesis and dysregulation posit UCSD as an excellent location for Dr. Stachura to develop during the mentored phase of his award, and will be instrumental in laying the groundwork for the future success of these studies.